Biological processes both aerobic and anaerobic are widely used in treatment of wastewater for its sanitation; the aerobic processes are performed usually on the upper part of water treatment tanks, where it is required aerators to enable aerate the water; therefore are used biological contact rotors (RBC) that in the early steps perform degradation of organic matter remaining of the water from an anaerobic treatment and in the later stages enables the growth of different nitrifying bacteria (Nitrosomonas and nitrobacter) which convert ammonia nitrogen to nitrites and then to nitrates that will be converted to nitrogen gas in the anoxic zone. The rotors consist of a plastic medium clamped by a steel structure to a central shaft which rotates constantly, so that the discs remain immersed about 40% and the medium remains in intermittent contact with water and air. Said steel structure defining a cylindrical frame with a rotating shaft driven by a motor and mounted on the upper part of a wastewater treatment tank, in said cylindrical frame are fixed or are mounted, packs of media which consist of a supporting means of biofilm for bacterial growth.
Existing rotors use as fixation means of biofilm, different elements as PVC tubes, high density polyethylene sheets or polypropylene to form a disc to be immersed up to 40% into the water of a wastewater treatment tank and the media remains in intermittent contact with water and air. Thus are created optimal conditions for microorganism growth on the media capable of degrading the organic matter contained in wastewater.
Thus are created optimal conditions for microorganism growth on the media to form a biofilm up to 5 mm capable of degrading the organic matter contained in wastewater. Existing rotors use as fixation means of biofilm different elements as PVC tubes, high density polyethylene sheets or polypropylene, all this forming a disc.
The problem with these conventional rotors is when are assembled, the fixing of the media are directly effected on the ring structure by means of fixing of steel elements supporting the media by using “Q” clamps, and screws, leaving the media in some cases permanently fixed.
The assembly of conventional rotors is carried out by structural members as “CPS” channels, which are assembled at the work site and its design consists of a simple arm to accommodate each one of the packages or sections of media, that is, for each end of the package is required a separate clamping arm; therefore the number of arms is equal to twice the number of packages to be placed. The circular ring formed by the set of these arms is formed by structural members as “L” angles independent from the arms.
Furthermore, the conventional arm designs have shortcomings regarding the scope of installation.
In the prior art the U.S. Pat. No. 4,385,987 of Charles M. McGinley, et al issued on May 31, 1983, which discloses an apparatus for wastewater treating including a rotating disc assembly partially immersed in a tank containing wastewater was found. The disc assembly includes a plurality of lightweight non-metallic discs, each disc comprising a plurality of similar disc sections. Adjacent discs of the disc assembly are coupled to each other and each disc has a surface configuration which cooperates with the next adjacent disc surface configuration to define a plurality of concentric passages between the discs. A plurality of elongated rigid bars secures the disc through joints to a pair of circular end supporting members and to the circular intermediate supporting members.
The rotor includes a polygonal shaft 18 in which are fixed supporting discs 29, including shaft central elements 30 which consist of a circular flat plate 31 having a plurality of grooves 35 and a polygonal central hole 32 to fit on the polygonal shaft 18. Each of the supporting discs comprises a plurality of elongated bars 34 projecting from the grooves 35 of the circular plate 31. The bars are radially projected and secured at its outer end to a ring member 36 with solder.
Semicircular packages 41 are mounted between said supporting elements 29 comprising the outer rings 36, said packages 41 being attached through a plurality of elongated plastic rods in the outer zone 63 protruding in the outer part and a plurality of rods in the protruding inner zone 64. Outer support rods 63 are fixed to the elements 59 fixed to the outer ring 36, while the inner rods 64 are projected through the supporting element, deeper in each section of the inner disc 36. Each end of the outer support rod 63, has a coupling flexible element 65 secured thereto.
Again is shown that packages are fixed exclusively with rods which are attached directly to the outer ring 36 and in the inner circular flat plate 31; so that to disassemble an intermediate package, must be removed the entire structure so as to detach the inner rods of the lower area. Furthermore, the mounting and dismounting operations are extremely complicated and require labor intensive.
It was also found the U.S. Pat. No. 4,444,658 of Robert W. Hankes and Lloyd H. Parker dated on Apr. 24, 1984 and which discloses a contact biological rotor comprising a tank, a shaft mounted for rotation in said tank, means for rotating said shaft and a plurality of frame assemblies. The shaft has a plurality of bayonet terminal rows. Each frame is adapted to be secured to one row spaced apart of terminals and is adapted to be mounted to the contactor. According to FIG. 3, the shaft comprises fixing flanges of a plurality of annular elements adapted to fix a plurality of L-shaped radial arms joined each other by means of tensioner arms, and said radial arms receive longitudinal braces which link packages to provide greater structural strength.
However, the L-shaped radial arms do not have the same configuration, or the same structure of the rotor, nor are assembled from structural arms compared with the present invention.
In FIGS. 7 and 8 also are shown semicircular packages 30 (media) formed by semicircular segments which are fixed by bolts 37 directly to the radial arms of the rotor; the semicircular segments have radial ribs which define pie shaped segments 34a, 34b and 34c, but the body of the package sheets remains semicircular, so that two semicircular packages are needed to form the rotor disc, and wherein said packages are directly fixed to the structural radial arms fixed at the rotation shaft.
There are several patents wherein are used segments of sheets or plates in the form of “pies” or slice of cake to form the media, for the assembling of the aeration rotor at wastewater treatment plant; but in all cases, these segments of sheets or plates in the form of “pies” are fixed directly to the structural arms radially arranged on the rotors and/or on arms or braces that attach said radial arms at their ends, so that when is required to change the media, must be disassembled whole structure of the rotor, as in the case of the U.S. Pat. No. 4,149,972 and EP0366477A1.
Was found the U.S. Pat. No. 4,692,241 of John L. Nicholson issued on Sep. 8, 1987, which discloses a biological rotor for treatment of biomass in a wastewater treatment plant, said rotor comprises packages 40, comprising biomass support sheets 41, 42, the package 40 being supported between support assemblies 43, 44 each of which comprises a circular ring 43a, 44a and a number of channel-shaped arms, 43b and 44b. The arms of each support assembly are bolted at its inner end to a radial flange (43c, 44c) of the rotor shaft 25, and at its outer end in the respective ring 43a, 44a and disposed in axial pairs along the shaft 25 such that for each adjoining pair of supporting assemblies, these pairs of arms 43b, 44b are in axial plane with their channels confronted.
Each package 40 includes a large number of biomass support sheets 41, 42 (typically 50 or more) that are threaded through the tubes 45, 46, 47. Each sheet 41, 42 has a slit 49 surrounding the hole where the respective tube 45-47 is located and has diagonal ribs/grooves 50 to harden the plastic sheets and to separate adjacent sheets.
The tubes 46 and 47 traverse the plurality of sheets 41, 42 at their upper part and are directly fixed to the circular rings 43a, 44a through the U-shaped supports, 52; likewise, the tubes 45 are fixed directly to the arms, 43b, 44b. 
This way of fixing these packs of media cause that when must be exchanged or provide maintenance to these, all packs of media must be disassembled, implying many drawbacks in terms of maneuvers, costs, labor, management, etc.
Each tube 45 is sized so that the opposite ends slide within channels of a respective coplanar pair of arms 43b, 44b and a web plate 51 is provided in each channel.
The ends of the two tubes 46, 47 enter into the circumference of the rings 43a, 44a and can be fixed there with a U-shaped support 52.
Other related documents are U.S. Pat. No. 4,608,162, EP0366477, MX/a/2008/005486, MX167652, MX9404071, MX185983, which are only cited as reference of rotor structures of similar constructions, wherein are used structural arms L-shaped, T-shaped or U-shaped; but none of them shows, exhibits, or suggests a structural supporting arm for assembly of aeration rotor at wastewater treatment plant as that of the present invention.
Existing rotors have a structure that does not allow accommodate large number of media and wastes a lot of space. Furthermore, the installation of the rotor is slow and difficult, because it is performed entirely in the field or if it is armed and subsequently is transported to the work site, the transfer limits the size of the rotor (diameter and length).
Within the biological contact rotor (BCR), shaft is the structural member disposed to support the entire load or weight of the entire system such as the structural members, the polyethylene media, the biomass created during the biological process and all other accessories such as screws and rivets.
To design a shaft of a biological contact rotor, should be kept in mind that this component must be sufficiently strong, but at the same time should be optimized the design so that the weight does not increase and add more weight to the structure. That is, the problem is to reduce the weight of the shaft without sacrificing load strength. For this, is necessary an optimum structure of the rotor frame and an optimum fixation system of various elements of the rotor structure in order to avoid deformations due to flexion and/or deflection as a result of the load generated by the rotor structure itself, by the polyethylene media mounted on the rotor, by the biomass created during the biological process and all other accessories such as screws and rivets.
In the cited documents are also disclosed plates for media in the form of “pies” or slice of cake; but said plates usually are set by fixation means directly to the radial arms of the rotation axes of the rotors and in other transverse or diagonal arms, or braces joining said radial arms and in other cases are directly fixed to the outer and inner rings of the rotor support structures; such fixing ways involve a number of operations, logistics, costs, handling and excessive maneuvering among other difficulties that occur during transportation and installation; also, the individual components generate confusion at the work site by having a large number of individual pieces, which also demands a large work area which in many cases is not available.
Therefore, the present invention is directed to a high capacity biological contact rotor, for wastewater treatment, that enables a solid, stable, resistant and lightweight frame; with a novel fixation system of packs of media; which also allows greater density or concentration of mediums per meter, provides an alternative that allows improve the aerobic process of removing the polluting organic load for optimal sanitation of wastewater, which is achieved in a practical, economical and modular way.